1. Field
The invention relates to an accessory device for a performance-monitoring device, wherein the performance monitoring relates to measuring heart rate information non-invasively.
2. Description of the Related Art
Nowadays people are increasingly concerned about their own health and physical endurance. One way to ease the concern is to provide means for monitoring heart rate non-invasively with a device or system designed for that purpose. The monitoring can be performed during physical exercise or it can be done, for example, while watching a TV-program.
An exemplary system designed for that purpose includes a transmitter and a receiver, wherein the transmitter is typically a belt worn around the chest of a user, and the receiver can be, for example, a wrist computer. A detector in the transmitter detects the heart rate of the person and transmits information to the receiver that is capable of processing the received information and displaying it to the user.
Heart rate can be measured from an electrocardiogram (ECG) signal of the user. The ECG signal is an electromagnetic signal generated by the heartbeat of a human and detectable on the skin of the human. Generally, the belt worn by the user comprises two electrodes that are in electrical contact with the skin of the user in order to measure the electromagnetic ECG signal. The detector of the belt is able to detect the potential difference between the two electrodes. From this information, the processor of the transmitter/receiver may generate heart rate information and display it to the user via a display.
The usability of the belt as a transmitter is not an ideal solution. It takes time to put on the belt around the chest, and the belt may the belt may cause discomfort. On the other hand, if the belt is too loose the electric contact between the electrode and the skin is not sufficient for reliable ECG detection. The ability to instantly check the heart rate by using the belt as an ECG detector requires that the belt is worn. Therefore, the belt should be at least carried with the user all the time so that the user can put it on when desired. Thus, a more practical solution for instantly checking the heart rate is needed.